It is known that three-dimensional epoxy-amine networks produced by curing epoxy compositions that contain a liquid epoxy resin and amino hardeners normally exhibit desirable properties. Therefore, amine-curable epoxy resin systems find wide application in the industry as coatings, adhesives, sealants, or matrices for components. Some applications require increase in the reaction rate which is normally achieved by adding accelerators. Various accelerators, such as phenol compounds, benzyl alcohol, carboxylic acids etc., are currently used by the industry to accelerate the curing process with commonly used amines and amine adducts. As these accelerators migrate from the cured epoxy polymer during the use, physical properties of that polymer are changed. The accelerators also act as plasticizers to the epoxy matrix and reduce the chemical resistance of the resulting cured epoxy polymer. A particular problem exists with the use of phenol as an accelerator, since it is highly corrosive to skin and is coming under an increasing regulatory pressure. Furthermore, the effect of phenol, nonyl phenol, benzyl alcohol and acids as accelerators are limited in their influence on a cure rate or physical and chemical properties of the resulting cured epoxy product.
Other currently used accelerators include tertiary amines such as trisdimethylaminomethylphenol (Ancamine K-54 by Air Products and Chemicals, Inc., PA, USA.), 1-2-aminoethyliperazine—(Accelerator 399 by Huntsman Corp., TX, USA), and acids such as salicylic acid, toluenesulfonic acid and boron trifluoride. Mercaptanes often are used for very rapid cure of epoxy formulations. However they are fugitive and can effect the environment.
Many accelerators are being developed in order to overcome these difficulties. However there is always a need for new accelerators and modifiers that could provide acceleration of curing of epoxy-amine compositions and in addition could modify the properties without significant adverse effects. The presence of active hydroxyl groups contained in hydroxyurethane compounds suggests an accelerating effect. The hydroxyurethane (another named hydroxylalkyl urethane or hydroxylalkyl carbamate) compounds are formed as a result of a reaction of cyclic carbonate with amine functionalities and well known in epoxy materials techniques.
Introduction of hydroxyurethane groups into a matrix of epoxy compound is described, for example, in the review “Cyclocarbonate Based Polymers Including Non-Isocyanate Polyurethane Adhesives and Coatings” by Oleg Figovsky and Leonid Shapovalov in Encyclopedia of Surface and Colloid Science, Second Edition; Taylor & Francis: New York, 2006; Vol. 3, pp. 1633-1652; and U.S. Pat. No. 7,232,877 issued to O. Figovsky, L. Shapovalov in 2007. In the above compounds, polyepoxy components, polyamine components and polycyclocarbonate components are combined by chemical bonds into common network. However, although such hybrid non-isocyanate polyurethane (HNIPU) materials have improved mechanical properties, they still possess certain shortcomings. More specifically, they demand preparation of special amine-cyclocarbonate adducts on the initial phase of processing. These reactive adducts are not stable due to an aminolysis reaction that increases viscosity during storage. Such a reaction is described in the article “A new route to polyurethanes from ethylene carbonate, diamine and diols” by G. Rokicki and A. Piotrowska in Polymer, 2002, Vol. 43, No. 10, pp. 2927-2935. Furthermore, alkylcyclocarbonates can be introduced only in limited quantities.
Numerous references exist showing the reactions of primary and secondary amines with monocyclocarbonates, e.g., propylene carbonates, to yield corresponding hydroxypropyl urethanes. For example, the article “Polyurethane elastomers obtained without the use of diisocyanates” by L. Ya. Rappoport, G. N. Petrov, I. I. Trostyanskaya and O. P. Gavrilova in International Polymer Science and Technology, 1981, Vol. 8, No. 5, pp. T/68-T/70. The Rappoport et al. paper discloses generally the reaction of cyclic carbonates with amines to form polyurethane elastomers. These materials are synthesized by two methods: the interaction of oligomers, containing some cyclocarbonate groups per molecule with low-molecular diamines and reactions of monomeric cyclocarbonates with low molecular diamines to obtain urethane-containing glycols used subsequently as the basic component for synthesizing polyurethane acetals by reacting with divinyl ethers of glycols. The last process is described in detail in U.S. Pat. No. 3,929,731 issued to Volkova, et al. in 1975.
U.S. Pat. No. 4,484,994 issued to Jacobs III, et al. in 1984 describes a hydroxyalkyl urethane-containing resin having at least one tertiary amine and at least two hydroxyalkyl urethane groups per molecule. The polymer is obtained by reacting an epoxy resin having an average epoxy equivalent weight from about 300 to about 10,000 with one or more amines having at least one secondary amine group and at least one hydroxyalkyl urethane group or a precursor thereof. The resulting polymer is too viscous and demands the use of organic solvents and increased temperatures.
U.S. Pat. No. 4,520,167 issued to Blank, et al. in 1985 discloses a coating composition comprises a hydroxyalkyl urethane compound, an amide-aldehyde cross-linker, a polymer containing active sites which are reactive with the cross-linker and, optionally, an acid catalyst. The hydroxyalkyl urethane compound serves as a reactive diluent in the composition. The composition is stable at ambient temperature and reactive only at elevated temperature to form a cross-linked compound in which the hydroxyalkyl urethane compound is chemically incorporated.
U.S. Pat. No. 4,631,320 issued to Parekh, et al. in 1986 relates to a thermostable coating composition that comprises a hydroxy group-containing polyurethane, polyurea, or polyurethane/polyurea polymer, an amino cross-linker, and, optionally, a catalyst and/or solvent. The polymer is obtained by self condensation of a hydroxyalkyl urethane compound or condensation of such a compound with a polyol and/or a polyamine. An applied coating of the composition is cured by heating to a predetermined temperature, e.g., from about 93° to about 204° C.
U.S. Pat. No. 4,758,632 issued to Parekh, et al. in 1988 describes a self-cross-linkable acrylic polymer that contains at least two hydroxyalkyl urethane groups per molecule and may comprise a reaction product of an acrylic backbone polymer containing one or more suitable reactive groups and an amine containing one primary or secondary amine group and at least one hydroxyalkyl urethane group or a precursor thereof. Alternatively, a self-cross-linkable polymer may be obtained by polymerization of an acrylic polymerizable monomer containing at least one hydroxyalkyl urethane group. A method of making the acrylic polymer, which is heat curable (≧122° C.) to provide thermosetting solvent-born coatings, comprises reacting a monomer or backbone polymer with an amine that contains hydroxyalkyl urethane groups or precursors thereof in the presence of a catalyst.
U.S. Pat. No. 4,820,830 issued to Blank, et al. in 1989 discloses a hydroxyalkyl urethane produced by reacting a cyclic carbonate with an alkylene diamine of the formula: H2N-(A-)-NH2, wherein A is a cycloalkylene group or a branched chain alkylene moiety having from 4-18 carbon atoms, said moiety having attached thereto at least one alkyl group. Polymers of the resulting hydroxyalkyl urethanes are formed by reacting, e.g., with diols, polyols, or esters.
U.S. Pat. No. 4,897,435 issued to Jacobs III, et al. in 1990 relates to a hydrophilic, substantially epoxy-free self-cross-linkable polymer that contains hydroxyalkyl urethane groups and one or more tertiary amine groups. The polymer is made by reacting an epoxy resin having an average epoxy equivalent weight from about 100 to about 700 with one or more amines having at least one secondary amine group and at least one hydroxyalkyl urethane group or precursor thereof. A coating composition comprises an aqueous medium containing the polymer and, optionally, a cross-linking catalyst. A low temperature-curable coating is attained by utilization of the polymer with a suitable quaternary or ternary compound catalyst.
U.S. Pat. No. 5,134,205 issued to Blank in 1992 discloses certain polyamine hydroxyalkyl urethane monomers, polymers, and copolymers thereof and blends of the same with crosslinking film-making agents and films thereof deposited on substrates. Crosslinking agents are selected from the group consisting of a methylol polyamine and a polyisocyanate compound, or from the group consisting of a polyol, polycarboxylic acid, polycarboxylic acid ester, and polycarboxylic anhydride.
U.S. Pat. No. 5,565,531 issued to Blank in 1996 relates to improved acid etch resistant polymers and coatings, and their method of preparation. Polyurethane polyols that are used in this method have long alkyl side chains that include a single ether group. Therefore, when such polyurethane polyols react with melamine compounds, such as hexakismethoxymethylmelamine, they form coatings that have excellent solubility in hydrophobic solvents and provide films with excellent acid etch resistance.
U.S. Pat. No. 7,288,595, issued in 2007 to Swarup, et al. discloses a reaction product having polyether urethane groups formed from a polyoxyalkylene amine and a cyclic carbonate used in an equivalent ratio ranging from 1:0.5 to 1:1.5. Further provided is a process for preparing the aforementioned reaction product. The aforementioned invention also is aimed at obtaining an improved curable coating composition that includes a polymer that contains a reactive functional group and a curing agent having functional groups reactive with the functional groups of aforementioned polymer. The improvement consists of the introduction of the reaction product into the coating composition. Curing of the coating composition is carried out at an elevated temperature (121° C.).
U.S. Pat. No. 4,931,157 issued in 1990 to Joseph Valco, et al. teaches a product comprising an epoxy resin and a hydroxyalkyl-substituted urethane. Preferred polyepoxides are glycidyl ethers of polyphenols such as bisphenol A. Hydroxy-substituted urethanes are prepared by reacting a 1,2-polyol with a polyisocyanate. The reaction products have the following structural formula, wherein x preferably equals 1:

Polyamines such as ethylene diamine are included to incorporate cationic groups into the epoxy resin. Hydroxyalkyl-substituted urethanes are used as chain extenders for epoxy resins at the presence of catalysts and solvents at 100-145° C.
U.S. Pat. No. 3,305,527 issued in 1967 to Herbert Price teaches combining epoxide resins with 1,2-alkylene carbonates and primary amine curing agents such as ethylene diamine.
Thus, all known polymer compositions with hydroxyalkyl urethane monomers demand specific chemical reactions (such as transetherification, transamination, or self-cross-linking). These reactions are carried out at elevated temperatures, in the presence of organic solvents, and/or in water-dispersion media, sometimes in the presence of catalysts.
U.S. Pat. No. 5,235,007 issued in 1993 to David Alexander et al., teaches an epoxy resin compositions cured with mixtures of di-primary amines and carbamates, which are the reaction products of di-primary amines with alkylene glycol carbonates. The mixtures lead to faster curing, giving cured resins with improved properties, than may be observed after curing with di-primary amines alone. Preferred di-primary amines are ethylene amines, oxyalkylene amines, cycloaliphatic or araliphatic amines or alkylene diamines. Preferred carbonates are ethylene or propylene glycol carbonate.